This plastic Futaba servo wheel is made to match Futaba servo splines, such as those on the SpringRC SM-S4303R and Power HD AR-3606HB continuous rotation servos. The wheel is molded from ABS and measures just under 2-5/8" across by 0.3" wide. With the included rubber band tire, the total wheel diameter is 2-5/8". The wheel is available in blue, yellow, red, and black.